I tried it with a song from Shatter. You can see where it got stuck. Also if it gets pissy because you changed tabs, pull the tab out into it's own browser thingy and it won't have a problem being in the background.

I just noticed the Tune button. I've only messed with it a little, but about 20 seconds and I was already able to make the song sound better by reducing skipping and dirty seams. Also you can delete branches by highlighting them and pressing Delete on your keyboard. Drop the threshold under Tune, and delete problem branches, and you'll end up with something that sounds far better and looks a lot less like the picture I posted.